Methods of counteracting gravitational forces on the human body have been devised for therapeutic applications as well as physical training. One way to counteract the effects of gravity is to suspend a person using a body harness to reduce ground impact forces. However, harness systems may cause pressure points that may lead to discomfort and sometimes even induce injuries. Another approach to counteract the gravity is to submerge a portion of a user's body into a water-based system and let buoyancy provided by the water offset gravity. However, the upward supporting force provided by such water-based systems distributes unevenly on a user's body, varying with the depth of the user's body from the water surface. Moreover, the viscous drag of the water may substantially alter the muscle activation patterns of the user.
Described herein are various embodiments of differential air pressure systems and methods of using such systems. The differential air pressure system may comprise a chamber configured to receive a portion of a user's lower body and to create an air pressure differential upon the user's body. The differential air pressure system may further comprise a user seal that seal the pressure chamber to the user's body. The height of the user seal may be adjusted to accommodate users with various body heights.